The band's Max George said: "This song is about a day in your life that you never forget. It's an upbeat, feel-good track and our favourite so far. We're really excited to get it out there, and delighted that it is supporting such a great cause."

The boyband, whose self-titled debut album went top-five last year, follow in the footsteps of groups including the Spice Girls and Girls Aloud who have recorded singles for the biennial fundraising event.

They will also perform the track on Friday night during BBC One's coverage of Comic Relief. The show's presenters will include James Corden, Davina McCall, Michael McIntyre and Jonathan Ross.

Among the celebrities helping to raise funds this year are daredevil Blue Peter presenter Helen Skelton who walked a high-wire suspended above Battersea Power Station to raise money.

Former deputy prime minister Lord Prescott will read the Radio 4 shipping forecast on Saturday March 19 to support the charity.

Other big names helping out include stars from the political comedy The Thick Of It and Peep Show's Robert Webb who are joining a Twitrelief auction which will see more than a hundred prolific Tweeters and celebrities taking part.

They will sell off "follows", which means the celebs will subscribe to the messages of the highest bidder. And many of them are throwing in extras.

Funnyman Chris Addison is offering an "abusive phone call" with him and Thick Of It co-star Malcolm Tucker (Peter Capaldi) in the Twitter auction. Others taking part include Simon Pegg, JLS, Jamie Oliver and Sarah Brown, wife of former prime minister Gordon Brown.